Implant recharger handshaking system and method

ABSTRACT

Systems, methods, and devices for wireless recharging of an implanted device. In response to receiving identification information from an implanted device, a charger can set an electrical field to a first field strength and receive first field strength information from the implanted device. The charger can then set the electrical field to a second field strength and receive second field strength information from the implanted device. This information relating to the first and second field strengths can be used to determine whether to recharge the implanted device.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/270,092, entitled “IMPLANT RECHARGER HANDSHAKING SYSTEM AND METHOD,”and filed on May 5, 2014, which claims the benefit of U.S. ProvisionalApplication No. 61/819,453, entitled “IMPLANT RECHARGER HANDSHAKINGMECHANISM,” and filed on May 3, 2013, the entirety of both which arehereby incorporated by reference herein.

BACKGROUND

The prevalence of use of medical devices in treating ailments isincreasing with time. In many instances, and as these medical devicesare made smaller, these medical devices are frequently implanted withina patient. To the extent that these devices use an implanted powersource to power themselves, the recharging of the implanted power sourcecan be a frequent and tedious task.

In many instances, device and tissue heating can be a significantconcern with rechargeable, implantable medical devices. These heatingconcerns particularly arise during recharging. Specifically if thecharge field is too weak, the implantable medical device will notquickly recharge, however, if the charge field is too strong, theimplantable medical device may overheat, thereby causing implanteediscomfort, and potentially injuring the implantee. Accordingly,systems, methods, and devices are desired to improve recharging ofimplantable medical devices.

BRIEF SUMMARY

One aspect of the present disclosure relates to a method of charging anenergy storage device of an implantable pulse generator using anexternal charger. The method includes wirelessly receiving at theexternal charger an identifier corresponding to the implantable pulsegenerator, wirelessly receiving at the external charger information fromthe implantable pulse generator corresponding to a first sensedelectrical field strength, at the external charger, changing thestrength of the electrical field, after changing the strength of theelectrical field, wirelessly receiving at the external chargerinformation from the implantable pulse generator corresponding to asecond sensed electrical field strength, and in response to the receivedinformation corresponding to the first and second sensed electricalfields, charging the energy storage device of the implantable pulsegenerator using the external charger.

In some embodiments, the method includes setting a first strength of theelectrical field at the external charger, and in some embodiments, thefirst strength of the electrical field set at the external charger iszero, while in other embodiments, the first strength of the electricalfield set at the external charger is non-zero. In some embodiments,charging the energy storage device of the implantable pulse generatorfurther includes changing the strength of the electrical field to athird strength at the external charger. In some embodiments, the methodincludes determining the third strength of the electrical field, whichthird strength of the electrical field can be, for example, determinedbased on at least one of: a parameter of the implantable pulsegenerator, the external charger information corresponding to a firstsensed electrical field strength, and the external charger informationcorresponding to the second sensed electrical field strength.

In some embodiments of the method, the parameter of the implantablepulse generator identifies one of: a charge state of the energy storagedevice, a temperature, a shunt current, and a maximum charge rate of theenergy storage device. In some embodiments, the method includesterminating charging when a desired charge state is achieved. In someembodiments, the desired charge state is determined from one of atemperature and a shunt current.

One aspect of the present disclosure relates to a wireless chargingsystem. The wireless charging system includes an implantable pulsegenerator. The implantable pulse generator can include an energy storagedevice. In some embodiments, the implantable pulse generator cantransmit information concerning: (i) a first sensed electrical fieldstrength at a first time. and (ii) a second sensed electrical fieldstrength at a second time. In some embodiments, the system can includean external charger that can receive the transmitted information fromthe implantable pulse generator and initiate charging of the energystorage device when the transmitted information about the first andsecond sensed electrical field strength corresponds to information aboutthe state of an electrical field generated by the external charger atthe first and second times.

In some embodiments, the external charger can vary the strength of theelectrical field based on information received from the implantablepulse generator. In some embodiments, the information received from theimplantable pulse generator identifies one of a charge state, a shuntcurrent, and a temperature. In some embodiments, the external chargercan change the state of the electrical field to a third strength duringcharging of the energy storage device. The external charger can, forexample, determine the third strength of the electrical field based onat least one of: a parameter of the implantable pulse generator, thetransmitted information concerning the first sensed electrical fieldstrength at the first time, and the transmitted information concerningthe second sensed electrical field strength at the second time.

In some embodiments of the system, the implantable pulse generator cantransmit data relating to at least one of: temperature; and a chargestate during the charging of the energy storage device. In someembodiments, the external charger can terminate charging when one of: atemperature threshold is exceeded, and a desired charge state isattained.

One aspect of the present disclosure relates to a method of charging anenergy storage device of an implantable pulse generator using anexternal charger. The method can include wirelessly receiving at theexternal charger an identifier corresponding to a first implantablepulse generator, wirelessly receiving at the external chargerinformation from the first implantable pulse generator corresponding toa first sensed electrical field strength, at the external charger,changing the strength of the electrical field, after changing thestrength of the electrical field, wirelessly receiving at the externalcharger information from the first implantable pulse generatorcorresponding to a second sensed electrical field strength, and inresponse to the received information corresponding to the first andsecond sensed electrical fields, determining not to recharge the firstimplantable pulse generator.

In some embodiments, the method includes determining an inability torecharge the first implantable pulse generator based on the informationcorresponding to the first sensed electrical field. In one exemplaryembodiment, the inability to recharge the first implantable pulsegenerator can be determined if the information corresponding to thefirst sensed electrical field indicates a source of the electrical fieldother than the external charger. The method can include, selecting asecond implantable pulse generator based on a first sensed electricalfield strength at the second implantable pulse generator and a secondsensed electrical field strength at the second implantable pulsegenerator, and charging the second implantable pulse generator.

In some embodiment of the method, charging the second implantable pulsegenerator can include changing the strength of the electrical field sothat the electrical field is detectable by the second implantable pulsegenerator and is not detectable by the first implantable pulsegenerator. In one exemplary embodiment, the method can include comparingthe information corresponding to the second sensed electrical field to athreshold, and determining that the sensed electrical field is too weakto recharge the first implantable pulse generator. The method caninclude selecting a second implantable pulse generator based on a firstsensed electrical field strength at the second implantable pulsegenerator and a second sensed electrical field strength at the secondimplantable pulse generator, and charging the second implantable pulsegenerator. In some embodiments, charging the second implantable pulsegenerator can include changing the strength of the electrical field sothat the electrical field is detectable by the second implantable pulsegenerator and is not detectable by the first implantable pulsegenerator.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating various embodiments, are intended for purposes ofillustration only and are not intended to necessarily limit the scope ofthe disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one embodiment of an implantableneurostimulation system.

FIG. 2 is a schematic illustration of one embodiment ofinterconnectivity of the implantable neurostimulation system.

FIG. 3 is a schematic illustration of one embodiment of the architectureof the external pulse generator and/or of the implantable pulsegenerator that is a part of the implantable neurostimulation system.

FIG. 4 is a schematic illustration of one embodiment of the charger thatis a part of the implantable neurostimulation system.

FIG. 5 is a flowchart illustrating one embodiment of a process forcharging a pulse generator.

FIG. 6 is a flowchart illustrating one embodiment of a process forcontrolling charging of the pulse generator.

FIG. 7 is a flowchart illustrating one embodiment of a process forcharge monitoring.

In the appended figures, similar components and/or features may have thesame reference label. Where the reference label is used in thespecification, the description is applicable to any one of the similarcomponents having the same reference label.

DETAILED DESCRIPTION OF THE INVENTION

A significant percentage of the Western (EU and US) population isaffected by Neuropathic pain (chronic intractable pain due to nervedamage). In many people, this pain is severe. There are thousands ofpatients that have chronic intractable pain involving a nerve.Neuropathic pain can be very difficult to treat with only half ofpatients achieving partial relief. Thus, determining the best treatmentfor individual patients remains challenging. Conventional treatmentsinclude certain antidepressants, anti-epileptic drugs and opioids.However, side effects from these drugs can be detrimental. In some ofthese cases, electrical stimulation can provide effect treatment of thispain without the drug-related side effects.

A spinal cord stimulator is a device used to deliver pulsed electricalsignals to the spinal cord to control chronic pain. Because electricalstimulation is a purely electrical treatment and does not cause sideeffects similar to those caused by drugs, an increasing number ofphysicians and patients favor the use of electrical stimulation overdrugs as a treatment for pain. The exact mechanisms of pain relief byspinal cord stimulation (SCS) are unknown. Early SCS trials were basedthe Gate Control Theory, which posits that pain is transmitted by twokinds of afferent nerve fibers. One is the larger myelinated Aδ fiber,which carries quick, intense-pain messages. The other is the smaller,unmyelinated “C” fiber, which transmits throbbing, chronic painmessages. A third type of nerve fiber, called Aβ, is “non-nociceptive,”meaning it does not transmit pain stimuli. The gate control theoryasserts that signals transmitted by the Aδ and C pain fibers can bethwarted by the activation/stimulation of the non-nociceptive Aβ fibersand thus inhibit an individual's perception of pain. Thus,neurostimulation provides pain relief by blocking the pain messagesbefore they reach the brain.

SCS is often used in the treatment of failed back surgery syndrome, achronic pain syndrome that has refractory pain due to ischemia. SCScomplications have been reported in a large portion, possibly 30% to40%, of all SCS patients. This increases the overall costs of patientpain management and decreases the efficacy of SCS. Common complicationsinclude: infection, hemorrhaging, injury of nerve tissue, placing deviceinto the wrong compartment, hardware malfunction, lead migration, leadbreakage, lead disconnection, lead erosion, pain at the implant site,generator overheating, and charger overheating. The occurrence rates ofcommon complications are surprisingly high: including lead extensionconnection issues, lead breakage, lead migration and infection.

Peripheral neuropathy may be either inherited or acquired. Causes ofacquired peripheral neuropathy include physical injury (trauma) to anerve, viruses, tumors, toxins, autoimmune responses, nutritionaldeficiencies, alcoholism, diabetes, and vascular and metabolicdisorders. Acquired peripheral neuropathies are grouped into three broadcategories: those caused by systemic disease, those caused by trauma,and those caused by infections or autoimmune disorders affecting nervetissue. One example of an acquired peripheral neuropathy is trigeminalneuralgia, in which damage to the trigeminal nerve (the large nerve ofthe head and face) causes episodic attacks of excruciating,lightning-like pain on one side of the face.

A high percentage of patients with peripheral neuropathic pain do notbenefit from SCS for various reasons. However, many of these patientscan receive acceptable levels of pain relief via direct electricalstimulation to the corresponding peripheral nerves. This therapy iscalled peripheral nerve stimulation (PNS). As FDA approved PNS deviceshave not been commercially available in the US market, Standard spinalcord stimulator (SCS) devices are often used off label by painphysicians to treat this condition. A significant portion of SCS devicesthat have been sold may have been used off-label for PNS.

As current commercially-available SCS systems were designed forstimulating the spinal cord and not for peripheral nerve stimulation,there are more device complications associated with the use of SCSsystems for PNS than for SCS. Current SCS devices (generators) are largeand bulky. In the event that an SCS is used for PNS, the SCS generatoris typically implanted in the abdominal or in the lower back above thebuttocks and long leads are tunneled across multiple joints to reach thetarget peripheral nerves in the arms, legs or face. The excessivetunneling and the crossing of joints leads to increased post-surgicalpain and higher device failure rates. Additionally, rigid leads can leadto skin erosion and penetration, with lead failure rates being far toohigh within the first few years of implantation. Many or even mostcomplications result in replacement surgery and even multiplereplacement surgeries in some cases.

One embodiment of an implantable neurostimulation system 100 is shown inFIG. 1, which implantable neurostimulation system 100 can be, forexample, a peripherally-implantable neurostimulation system 10. In someembodiments, the implantable neurostimulation system 100 can be used intreating patients with, for example, chronic, severe, refractoryneuropathic pain originating from peripheral nerves. In someembodiments, the implantable neurostimulation system 100 can be used toeither stimulate a target peripheral nerve or the posterior epiduralspace of the spine.

The implantable neurostimulation system 100 can include one or severalpulse generators. A person of skill in the art will recognize thatalthough pulse generators are referred to herein as a recharged device,any implanted device can be recharged according to the systems andmethods disclosed herein. The pulse generators can comprise a variety ofshapes and sizes, and can be made from a variety of materials. In someembodiments, the one or several pulse generators can generate electricalpulses that are delivered to a nerve to control pain. One or both of thepulse generators can include a processor and/or memory. In someembodiments, the processor can provide instructions to and receiveinformation from the other components of the implantableneurostimulation system 100. The processor can act according to storedinstructions, which stored instructions can be located in memory,associated with the processor, and/or in other components of the contentinjection system 100. The processor can, in accordance with storedinstructions, make decisions. The processor can comprise amicroprocessor, such as a microprocessor from Intel® or Advanced MicroDevices, Inc.®, or the like.

In some embodiments, the stored instructions directing the operation ofthe processor may be implemented by hardware, software, scriptinglanguages, firmware, middleware, microcode, hardware descriptionlanguages, and/or any combination thereof. When implemented in software,firmware, middleware, scripting language, and/or microcode, the programcode or code segments to perform the necessary tasks may be stored in amachine readable medium such as a storage medium. A code segment ormachine-executable instruction may represent a procedure, a function, asubprogram, a program, a routine, a subroutine, a module, a softwarepackage, a script, a class, or any combination of instructions, datastructures, and/or program statements. A code segment may be coupled toanother code segment or a hardware circuit by passing and/or receivinginformation, data, arguments, parameters, and/or memory contents.Information, arguments, parameters, data, etc. may be passed, forwarded,or transmitted via any suitable means including memory sharing, messagepassing, token passing, network transmission, etc.

In some embodiments, the memory of one or both of the pulse generatorscan be the storage medium containing the stored instructions. The memorymay represent one or more memories for storing data, including read onlymemory (ROM), random access memory (RAM), magnetic RAM, core memory,magnetic disk storage mediums, optical storage mediums, flash memorydevices and/or other machine readable mediums for storing information.In some embodiments, the memory may be implemented within the processoror external to the processor. In some embodiments, the memory can be anytype of long term, short term, volatile, nonvolatile, or other storagemedium and is not to be limited to any particular type of memory ornumber of memories, or type of media upon which memory is stored. Insome embodiments, the memory can include, for example, one or both ofvolatile and nonvolatile memory. In one specific embodiment, the memorycan include a volatile portion such as RAM memory, and a nonvolatileportion such as flash memory.

In some embodiments, one of the pulse generators can be an externalpulse generator 102 or an implantable pulse generator 104. The externalpulse generator 102 can be used to evaluate the suitability of a patientfor treatment with the implantable neurostimulation system 100 and/orfor implantation of an implantable pulse generator 104.

In some embodiments, one of the pulse generators can be the implantablepulse generator 104, which can be sized and shaped, and made of materialto allow implantation of the implantable pulse generator 104 inside of abody. In some embodiments, the implantable pulse generator 104 can besized and shaped so as to allow placement of the implantable pulsegenerator 104 at any desired location in a body, and in someembodiments, placed proximate to a peripheral nerve such that leads(discussed below) are not tunneled across joints and/or such thatextension cables are not needed.

In some embodiments, the electrical pulses generated by the pulsegenerator can be delivered to one or several nerves 110 and/or to tissueproximate to one or several nerves 110 via one or several leads. Theleads can include conductive portions, referred to as electrodes, andnon-conductive portions. The leads can have a variety of shapes, can bein a variety of sizes, and can be made from a variety of materials,which size, shape, and materials can be dictated by the application orother factors.

In some embodiments, the leads can include an anodic lead 106 and/or acathodic lead 108. In some embodiments, the anodic lead 106 and thecathodic lead 108 can be identical leads, but can receive pulses ofdifferent polarity from the pulse generator. Alternatively, in someembodiments, each lead can alternatingly include anodic and cathodicelectrodes.

In some embodiments, the leads can connect directly to the pulsegenerator, and in some embodiments, the leads can be connected to thepulse generator via a connector 112 and a connector cable 114. Theconnector 112 can comprise any device that is able to electricallyconnect the leads to the connector cable 114. Likewise, the connectorcable can be any device capable of transmitting distinct electricalpulses to the anodic lead 106 and the cathodic lead 108.

In some embodiments, the implantable neurostimulation system 100 caninclude a charger 116 that can be configured to recharge the implantablepulse generator 104 when the implantable pulse generator 104 isimplanted within a body. The charger 116 can comprise a variety ofshapes, sizes, and features, and can be made from a variety ofmaterials. Like the pulse generators 102, 104, the charger 116 caninclude a processor and/or memory having similar characteristics tothose discussed above. In some embodiments, the charger 116 can rechargethe implantable pulse generator 104 via an inductive coupling.

In some embodiments, one or several properties of the electrical pulsescan be controlled via a controller. In some embodiments, theseproperties can include, for example, the frequency, strength, pattern,duration, or other aspects of the timing and magnitude of the electricalpulses. In one embodiment, these properties can include, for example, avoltage, a current, or the like. In one embodiment, a first electricalpulse can have a first property and a second electrical pulse can have asecond property. This control of the electrical pulses can include thecreation of one or several electrical pulse programs, plans, orpatterns, and in some embodiments, this can include the selection of oneor several pre-existing electrical pulse programs, plans, or patterns.In the embodiment depicted in FIG. 1, the implantable neurostimulationsystem 100 includes a controller that is a clinician programmer 118. Theclinician programmer 118 can be used to create one or several pulseprograms, plans, or patterns and/or to select one or several of thecreated pulse programs, plans, or patterns. In some embodiments, theclinician programmer 118 can be used to program the operation of thepulse generators including, for example, one or both of the externalpulse generator 102 and the implantable pulse generator 104. Theclinician programmer 118 can comprise a computing device that canwiredly and/or wirelessly communicate with the pulse generators. In someembodiments, the clinician programmer 118 can be further configured toreceive information from the pulse generators indicative of theoperation and/or effectiveness of the pulse generators and the leads.

In some embodiments, the controller of the implantable neurostimulationsystem 100 can include a patient remote 120. The patient remote 120 cancomprise a computing device that can communicate with the pulsegenerators via a wired or wireless connection. The patient remote 120can be used to program the pulse generator, and in some embodiments, thepatient remote 120 can include one or several pulse generation programs,plans, or patterns created by the clinician programmer 118. In someembodiments, the patient remote 120 can be used to select one or severalof the pre-existing pulse generation programs, plans, or patterns and toselect, for example, the duration of the selected one of the one orseveral pulse generation programs, plans, or patterns.

Advantageously, the above outlined components of the implantableneurostimulation system 100 can be used to control and provide thegeneration of electrical pulses to mitigate patient pain.

With reference now to FIG. 2, a schematic illustration of one embodimentof interconnectivity of the implantable neurostimulation system 100 isshown. As seen in FIG. 2, several of the components of the implantableneurostimulation system 100 are interconnected via network 110. In someembodiments, the network 110 allows communication between the componentsof the implantable neurostimulation system 100. The network 110 can be,for example, a local area network (LAN), a wide area network (WAN), awired network, a custom network, wireless network, a telephone networksuch as, for example, a cellphone network, the Internet, the World WideWeb, or any other desired network or combinations of different networks.In some embodiments, the network 110 can use any desired communicationand/or network protocols. The network 110 can include any communicativeinterconnection between two or more components of the implantableneurostimulation system 100. In one embodiment, the communicationsbetween the devices of the implantable neurostimulation system 100 canbe according to any communication protocol including, for example thosecovered by Near Field Communication (NFC), Bluetooth, or the like. Insome embodiments, different components of the system may utilizedifferent communication networks and/or protocols.

With reference now to FIG. 3, a schematic illustration of one embodimentof the architecture of the external pulse generator 102 and/or of theimplantable pulse generator 104 is shown. In some embodiments, each ofthe components of the architecture of the one of the pulse generators102, 104 can be implemented using the processor, memory, and/or otherhardware component of the one of the pulse generators 102, 104. In someembodiments, the components of the architecture of the one of the pulsegenerators 102, 104 can include software that interacts with thehardware of the one of the pulse generators 102, 104 to achieve adesired outcome.

In some embodiments, the pulse generator 102/104 can include, forexample, a network interface 300. The network interface 300 can beconfigured to access the network 110 to allow communication between thepulse generator 102, 104 and the other components of the implantableneurostimulation system 100. In some embodiments, the network interface300 can include one or several antennas and software configured tocontrol the one or several antennas to send information to and receiveinformation from one or several of the other components of theimplantable neurostimulation system 100.

The pulse generator 102, 104 can further include a data module 302. Thedata module 302 can be configured to manage data relating to theidentity and properties of the pulse generator 102, 104. In someembodiments, the data module can include one or several database thatcan, for example, include information relating to the pulse generator102, 104 such as, for example, the identification of the pulsegenerator, one or several properties of the pulse generator 102, 104, orthe like. In one embodiment, the data identifying the pulse generator102, 104 can include, for example, a serial number of the pulsegenerator 102, 104 and/or other identifier of the pulse generator 102,104 including, for example, a unique identifier of the pulse generator102, 104. In some embodiments, the information associated with theproperty of the pulse generator 102, 104 can include, for example, dataidentifying the function of the pulse generator 102, 104, dataidentifying the power consumption of the pulse generator 102, 104, dataidentifying the charge capacity of the pulse generator 102, 104 and/orpower storage capacity of the pulse generator 102, 104, data identifyingpotential and/or maximum rates of charging of the pulse generator 102,104, and/or the like.

The pulse generator 102, 104 can include a pulse control 304. In someembodiments, the pulse control 304 can be configured to control thegeneration of one or several pulses by the pulse generator 102, 104. Insome embodiments, for example, this information can identify one orseveral pulse patterns, programs, or the like. This information canfurther specify, for example, the frequency of pulses generated by thepulse generator 102, 104, the duration of pulses generated by the pulsegenerator 102, 104, the strength and/or magnitude of pulses generated bythe pulse generator 102, 104, or any other details relating to thecreation of one or several pulses by the pulse generator 102, 104. Insome embodiments, this information can specify aspects of a pulsepattern and/or pulse program, such as, for example, the duration of thepulse pattern and/or pulse program, and/or the like. In someembodiments, information relating to and/or for controlling the pulsegeneration of the pulse generator 100 to 104 can be stored within thememory.

The pulse generator 102, 104 can include a charging module 306. In someembodiments, the charging module 306 can be configured to control and/ormonitor the charging/recharging of the pulse generator 102, 104. In someembodiments, for example, the charging module 306 can include one orseveral features configured to receive energy for recharging the pulsegenerator 102, 104 such as, for example, one or several inductivecoils/features that can interact with one or several inductivecoils/features of the charger 116 to create an inductive coupling tothereby recharge the pulse generator 102, 104.

In some embodiments, the charging module 306 can include hardware and/orsoftware configured to monitor the charging of the pulse generator 102,104. In some embodiments, these features can be configured to monitorthe temperature of one or several components of the pulse generator 102,104, the rate of charge of the pulse generator 102, 104, the chargestate of the pulse generator 102, 104, or the like. These features caninclude, for example, one or several resistors, thermistors,thermocouples, temperature sensors, current sensors, charge sensors, orthe like.

The pulse generator 102, 104 can include an energy storage device 308.The energy storage device 308 can be any device configured to storeenergy and can include, for example, one or several batteries,capacitors, fuel cells, or the like. In some embodiments, the energystorage device 308 can be configured to receive charging energy from thecharging module 306.

With reference now to FIG. 4, a schematic illustration of one embodimentof the charger 116 is shown. In some embodiments, each of the componentsof the architecture of the charger 116 can be implemented using theprocessor, memory, and/or other hardware component of the charger 116.In some embodiments, the components of the architecture of the charger116 can include software that interacts with the hardware of the charger116 to achieve a desired outcome.

In some embodiments, the charger 116 can include, for example, a networkinterface 400. The network interface 400 can be configured to access thenetwork 110 to allow communication between the charger 116 and the othercomponents of the implantable neurostimulation system 100. In someembodiments, the network interface 400 can include one or severalantennas and software configured to control the one or several antennasto send information to and receive information from one or several ofthe other components of the implantable neurostimulation system 100.

In some embodiments, the charger 116 can include a data module 402. Thedata module 402 can be configured to manage data relating to theidentity and properties of the pulse generator 102, 104 with which thecharger 116 is communicating. In some embodiments, the data module 402can include one or several database that can include, for example, theidentification of the one or several pulse generators 102, 104 withwhich the charger 116 is communicating, one or several properties of theone or several pulse generators 102, 104 with which the charger iscommunicating, or the like. This information can include some or all ofthe information discussed above with respect to the data module 302.

The charger 116 can include a charging module 404. The charging module404 can be configured to control and/or monitor the charging of one orseveral of the pulse generators 102, 104. In some embodiments, forexample, the charging module 404 can include one or several protocolsthat can request information from the one or several pulse generators102, 104 at one or several times before, during, and after charging.This information can be received by the charger 116 from the pulsegenerator 102, 104 and can be used to control the generation of and/orproperties of the charge field. In some embodiments, the charging module404 can include one or several features configured to transmit energyfor recharging the pulse generator 102, 104 such as, for example, one orseveral inductive coils/features that can interact with one or severalinductive coils/features of the pulse generator 102, 104 to create aninductive coupling to thereby recharge the pulse generator 102, 104.

The charger 116 can include an energy storage device 406. The energystorage device 406 can be any device configured to store energy and caninclude, for example, one or several batteries, capacitors, fuel cells,or the like. In some embodiments, the energy storage device 406 can beconfigured to provide charging energy to the one or several pulsegenerators 102, 104 being recharged.

With reference now to FIG. 5, a flowchart illustrating one embodiment ofa process 500 for charging a pulse generator 102, 104 is shown. Theprocess 500 can be performed by and/or on a pulse generator 102, 104that can be, for example, in communication with the charger 116. Theprocess begins at block 501 wherein a nerve is stimulated. In someembodiments, the stimulation of the nerve can include the generation ofone or several pulses according to one or several pulse programs. Thiscan include retrieving information from, for example, the pulse control304 of the pulse generator 102, 104, and generation of pulses accordingto the pulse program retrieved from the pulse control 304. In someembodiments, these pulses can be delivered to one or several targetedareas that can include, for example, one or several targeted nerves viaelectrodes 106, 108. In some embodiments, the stimulation of block 501can be performed during the entire process 500, and in some embodiments,process 500 can be performed independent of the stimulation of block501. Thus, in some embodiments, process 500 may be performed whilestimulation occurs, when stimulation does not occur, or partially whilestimulation occurs.

After the nerve has been stimulated, the process 500 proceeds to block502 wherein an identification request is received. In some embodiments,the identification request can be received from the charger 116 via, forexample, the network interface 300. In some embodiments, theidentification request can be received as the first step in triggeringand/or initiating the charging of the pulse generator 102, 104. In someembodiments, the identification request can include a request forinformation identifying the pulse generator 102, 104, which informationcan include, for example, the serial number of the pulse generator 102,104.

After the identification request has been received, the process 500proceeds to block 504 wherein the identification of the pulse generator102, 104 is communicated. In some embodiments, this can include, forexample, retrieving information identifying the pulse generator 102, 104from the data module 302 of the pulse generator 102, 104. In someembodiments, this can further include the retrieval of informationrelating to one or several parameters of the pulse generator 102, 104such as, for example, the charge state of the energy storage device 308of the pulse generator 102, 104, one or several charging parameters ofthe pulse generator 102, 104 such as, for example, the rates with whichthe pulse generator 102, 104 can be charged, and/or the like. In someembodiments, the retrieved information can be combined into a messagewhich can be communicated from the pulse generator 102, 104 to thecharger 116 via the of the network interface 300 of the pulse generator102, 104.

The communication of the identification of the pulse generator 102, 104can be performed in response to the receipt of the identificationrequest in block 502, and in some embodiments, the communication of theidentification of the pulse generator 102, 104 can be periodicallyperformed without the receipt of the identification request of block502. In some embodiments, the communication of the identification can betriggered in response to the charge state of the energy storage device308 of the pulse generator 102, 104 including, for example, when thecharge state of the pulse generator 102, 104 drops below a thresholdvalue.

After the identification has been communicated, the process 500 proceedsto block 506 wherein a field property is determined. In someembodiments, the field property can be a property of a charging fieldand/or of an electric field detectable at the pulse generator 102, 104.In some embodiments, the determination of the field property can includean identification of the strength of the electric field and/or of thecharge field at one or several time points during the charging process.In some embodiments, the field property can be determined through theuse of components of the charging module 306 such as, for example, oneor several inductive coils, resistors, temperature sensors, or the like.In some embodiments, the field property may be determined in response toan instruction or a request from charger 116 or may be determined inresponse to a different trigger or in a predetermined manner.

After the field property has been identified, the process 500 proceedsto block 508 wherein the field property is communicated. In someembodiments, field property can be communicated to the charger 116 viathe network interface 300 of the pulse generator 102, 104. In someembodiments, the communication of the field property can include thegeneration of a message containing the field property and the sending ofthe generated message to the charger 116.

After the field property has been communicated, the process 500 proceedsto decision state 510, wherein it is decided if an additional fieldproperty should be determined. In some embodiments, for example, thepulse generator 102, 104 can receive a request from the charger 116 totake the second and/or other additional field property at one or severalother times during the charging process. Similarly, in some embodiments,the pulse generator 102, 104 can be configured to detect a second fieldproperty and/or multiple other field properties at one or several timeperiods during the charging process. Advantageously, the determinationof one or several additional field properties at one or severaladditional times during the recharging can allow verification and/oridentification of the ability of the charger 116 to manipulate and/orchange the charge field detected by the pulse generator 102, 104. Thiscan allow for better control during the recharging process.

If it is decided that an additional field property should be determined,whether via a request from the charger 116 and/or according to aprotocol of the pulse generator 102, 104, the process 500 returns toblock 506 and proceeds as outlined above. If it is decided that anadditional field property should not be determined, then the process 500proceeds to decision state 511, wherein it is determined if charging isinitiated. In some embodiments, the determination of the initiation ofcharging can include receiving an instruction to begin charging. In someembodiments, this instruction can be received from, for example, thecharger 116. In some embodiments, the determination of the initiation ofcharging can include detecting a property of the charging field enablingcharging, such as, for example, a strength of the charging field that isgreater than a threshold value, that is sufficiently large to allowcharging, or the like. If it is determined that charging is notinitiated, then the process proceeds to block 512 and continuesoperation. In some embodiments, the continued operation can include thecontinuing of the nerve stimulation identified in block 501, operatingaccording to one or several pulse programs, plans, or patterns,operating according to one or several new instructions received from,for example, the clinician programmer 118 and/or the patient remote 120,or the like.

Returning again to decision state 511, if it is determined that charginghas been initiated, then the process 500 proceeds to block 513, whereinthe energy storage device 308 is charged. In some embodiments, theenergy storage device 308 can be charged by energy received from theelectric field via the charging module 306.

In some embodiments, while the energy storage device 308 is beingcharged, the process 500 determines and/or monitors one or severalcharging parameters of the energy storage device 308. In someembodiments, this monitoring can occur throughout the charging of thepulse generator 102, 104 and the monitoring can occur, for example,once, multiply, periodically, and/or continuously. In some embodiments,these parameters can include, for example, temperature of the energystorage device 308, temperature of one or several components of thepulse generator 102, 104, a rate of charge of the energy storage device308, a charge state of the energy storage device 308, charge voltage,strength of charge field, amount of excess charge current, and/or thelike.

After the parameter of the charging has been determined, the process 500proceeds to block 516 wherein the charging parameter is compared to athreshold value. In some embodiments, this comparison of the chargingparameter to the threshold value can be used to determine whether toadjust a property of the field, whether to change the rate of chargingof the energy storage device 308, whether to stop the charging of theenergy storage device 308, and/or the like. In some embodiments, forexample, the threshold can be a temperature threshold, wherein atemperature above the threshold value is indicative of and/or cantrigger a request to decrease the strength of the charge field, a rateof charge threshold, wherein the rated charge threshold is specified bysome portion of the maximal and/or maximum charge rate of the pulsegenerator 102, 104, a charge state threshold, wherein the charge statethreshold indicates the charge state of the energy storage device 308 ofthe pulse generator 102, 104, a charge voltage threshold, a strength ofcharge field threshold, an amount of excess charge current threshold, orthe like.

After the charging parameter has been compared to a threshold, theprocess 500 proceeds to decision state 518 wherein it is determined ifthe charging is complete. In some embodiments, for example, thecompleteness of the charging can be determined based on the comparisonof the charging parameter to one of the thresholds such as, for example,a temperature threshold, a charge state threshold, or the like.

If it is determined that the charging is complete, then the process 500proceeds to block 520 wherein the completed charging is communicated. Insome embodiments, the communication to complete a charging can includethe generation of a message including information identifying thecompleted state of the charging by a processor of the pulse generator102, 104, and/or indicating the charge state of the energy storagedevice 308 of the pulse generator 102, 104. Thus, in some embodiments,the communication can comprise a command to stop charging and/or arequest to stop charging, and in some embodiments, the communication cancomprise information that can be used by the charger 116 to determinewhether to stop charging of the pulse generator 102, 104. In embodimentsin which the communication comprises data that can be used by thecharger 116 to determine whether to stop charging of the pulse generator102, 104, the process 600 can generate the communication directly afterdetermining the charging parameter in block 514. The communication canbe sent from a pulse generator to the charger 116 via, for example, thenetwork interface 300 of the pulse generator 102, 104.

Returning again to decision state 518, if it is determined that chargingis not complete, then the process 500 proceeds to decision state 522wherein it is determined if an adjustment of the charge field is desiredand/or indicated. In some embodiments, this can include, determining ifthe result of the comparison of a charging parameter to one of thethresholds indicates that the charging field and/or the strength of thecharging field should be either increased or decreased. In oneembodiment, for example, the comparison of a charging parameter relatingto the rate of charge of the pulse generator 102, 104 may indicate arate of charge that is lower than a rate of charge threshold. In onesuch embodiment, the pulse generator 102, 104 may request an increase inthe strength of the charging field. Similarly, in one embodiment, thecomparison of a rate of charge charging parameter relating to the rateof charge with the threshold for the rated charge may indicate that thecharging rate of the pulse generator 102, 104 is exceeding a thresholdvalue In one such embodiments, it may be determined that the strength ofthe charging field should be decreased. Similarly, in some embodiments,a temperature exceeding a threshold value may be an indicator of a needto decrease the charging field, a comparison of a charging parameterindicating the charge state with the charge state threshold may indicatethe need to decrease the strength of the charging field, or the like. Ifit is determined that the charging field does not need to be adjusted,then the process returns to block 514 and continues as outlined above.

If it is determined that the charging field should be adjusted, then theprocess 500 proceeds to block 524 wherein an adjustment request iscommunicated. In some embodiments, the communication adjustment requestcan include the creation of a message requesting the adjustment of thestrength of the charging field, and in some embodiments, the message cancomprise data, including one or several charging parameters determinedin block 514 that can be used by the charger 116 to determine whetherand how to adjust the charge field.

In some embodiments, the charging message may simply indicate whether toincrement or decrement the strength of the charging field, and in someembodiments, the adjustment message may indicate a degree to which thestrength of the charging field should be increased or decreased. Inembodiments in which the message comprises data, including one orseveral charging parameters determined in block 514 that can be used bythe charger 116 to determine whether and how to adjust the charge field,the process 600 can generate the message directly after determining thecharging parameters in block 514. In some embodiments, the adjustmentrequest can be communicated to the charger 116 from the pulse generator102, 104 via the network interface 300. After the adjustment request hasbeen communicated, or returning again to decision state 522, if it isdetermined that the charging field should not be adjusted, the process500 returns to block 514 and continues as outlined above.

In one exemplary embodiment, the process 500 can be implemented asfollows, the pulse generator 102, 104 can generate one or several pulsesto stimulate a nerve and/or portion of the patient's body. Whilegenerating the one or several pulses, the pulse generator 102, 104 canreceive an identification request and/or a charging request. In someembodiments, the pulse generator 102, 104 can retrieve informationrelating to the charge state of the energy storage device 308, anddetermine whether charging is desired and/or advisable. If charging isdesired and/or advisable, the pulse generator 102, 104 can retrieveidentification information from, for example, the data module 302 of thepulse generator 102, 104. This information can identify the pulsegenerator 102, 104.

After the pulse generator 102, 104 has received the identificationrequest, the pulse generator 102, 104 can generate a message includinginformation identifying the pulse generator 102, 104 and, in someembodiments, also including information relating to the pulse generator102, 104. In some embodiments, this information relating to the pulsegenerator 102, 104 can include information relating to the charge stateof the energy storage device 308, to acceptable rates of charge of thepulse generator 102, 104, and/or the like. This information relating tothe pulse generator 102, 104 and identifying the pulse generator 102,104 can be communicated to the charger 116 via, for example, the networkinterface 300.

After the identification information has been communicated to thecharger 116, the pulse generator 102, 104 can, according to one orseveral protocols stored on pulse generator 102, 104, or according to arequest received from the charger 116, determine a field property at afirst time. In some embodiments, the field property can include astrength of a charge field which can, for example, be at a first levelthat can be, for example, zero and/or close to zero. In someembodiments, a zero charge field can comprise a field having a strengthof less than 1 percent of the maximum charge strength, less than 5percent of the maximum charge strength, less than 10 percent of themaximum charge strength, and/or any other or intermediate value. Afterthe field property has been determined, the pulse generator 102, 104 cancommunicate the field property to the charger 116.

In some embodiments, after communicating the field property to thecharger, the pulse generator 102, 104 can determine a second fieldproperty at a second time. In some embodiments, the second fieldproperty can be determined in response to request received from thecharger 116 requesting information relating to a second field propertyat the second time, and in some embodiments, the second field propertycan be determined at the second time according to one or severalprotocols of the pulse generator 102, 104.

In some embodiments, after the second field property has been determinedat the second time, the pulse generator 102, 104 can communicate thefield property to the charger 116, and a signal initiating charging canbe received and/or charging can be initiated. In some embodiments, oneor several properties of the charge field and/or of the pulse generator102, 104 can be monitored during the charging, and these properties canbe compared to one or several thresholds to determine when to terminatecharging, and/or whether to adjust the strength of the charge field. Ifit is determined to terminate charging, then a message indicating thecompletion of the charging is generated and sent. Similarly, if it isdecided to adjust the strength of the charge field, then a messagerequesting an adjustment of the strength of the charge field isgenerated and sent.

With reference now to FIG. 6, a flowchart illustrating one embodiment ofa process 600 for controlling charging of the pulse generator 102, 104is shown. The process 600 can be performed by and/or on charger 116. Insome embodiments, the charger 116 can be, for example, in communicationwith the pulse generator 102, 104. The process 600 can begin a block602, wherein the charger 116 is powered. In some embodiments, thepowering of the charger 116 can occur when the charger 116 is turned on.

After the charger 116 is powered, the process 600 proceeds to block 604,wherein a query message is communicated. In some embodiments, the querymessage can comprise the identification request, and can include arequest for identification of any pulse generators 102, 104 receivingthe query message. In some embodiments, the query message can begenerated by the charger 116 and can be communicated to one or severalpulse generators 102, 104 via the network interface 400.

After the query message has been communicated, the process 600 proceedsto decision state 606, wherein it is determined if a response to thequery message has been received. In some embodiments, the response canbe the identification communication from block 504 of FIG. 5. In someembodiments, this determination can be made after a period such as, forexample, 0.5 seconds, 1 second, 2 seconds, 5 seconds, and/or any otheror intermediate length of time. If it is determined that no response hasbeen received, then the process 600 proceeds to block 616 wherein anerror is triggered and an error message is provided to the user. In someembodiments, the error message can indicate that no pulse generator 102,104 was found, and the error message can be displayed to the user.

Returning again to decision state 606, if it is determined that aresponse was received, then the process 600 proceeds to block 607wherein the charging frequency of the charger 116 is tuned by activelyadjusting the tuning frequency of the charger 116, and specifically ofthe features of the charging module 404. In some embodiments, thistuning can result in the components of the charging module 404 operatingat a frequency substantially equal to the resonant frequency of, forexample, the features of the charging module 306 of the pulse generators102, 104. This tuning can include measuring the output power of thecharging module 404 and reporting the output power to the processor ofthe charger 116. The actual power delivered to the charging module 306of the pulse generator 102, 104 can be measured and reported to thecharger 116. Based on the actual power delivered to the charging module306 of the pulse generator 102, 104 and the output power of the chargingmodule 404 of the charger 116, the charger 116 may adjust the tuningfrequency of the charging module 404 if the actual power delivered tothe receiving coil is not at a desired level. This may be repeated untilthe charger determines that the actual power delivered to the chargingmodule 306 of the pulse generator is at a desired level. In someembodiments, the tuning of block 607 can be performed before chargingstarts, at instance during charging, and/or continuously duringcharging. In some embodiments, the tuning of block 607 may be omittedfrom process 600.

The process 600 proceeds to block 608, wherein the charge field is setto first power and/or strength. In some embodiments, the charge fieldcan be sent to a low first power and/or strength. In some embodiments,the low first power and/or strength can be used to identify whether oneor several other charge fields can affect the charging of the pulsegenerator 102, 104. In some embodiments, the low first power cancomprise a power that is 0% of the maximum charge field strength and/orpower, 1% of the maximum charge field strength and/or power, 2% of themaximum charge field strength and/or power, 5% of the maximum chargefield strength and/or power, 10% of the maximum charge field strengthand/or power, 20% of the maximum charge field strength and/or power,and/or any other or intermediate percent of the maximum charge fieldstrength and/or power.

After the charge field has been set to the first strength and/or power,the process 600 proceeds to block 610 wherein charge field strength datais received. In some embodiments, the charge field strength data canidentify the strength of the charge field at the pulse generator 102,104. In some embodiments, the charge field strength can be detected withcomponents of the pulse generator 102, 104 including, for example,components of the charging module 306. The charge field strength datacan be received at the charger 116 via the network interface 400 of thecharger 116.

After the charge field strength data has been received, the process 600proceeds to decision state 612 wherein it is determined if the chargefield strength data indicates a detected charge field that is less thana threshold. In some embodiments, this comparison can identify whetherelectric fields from sources other than the charger 116 are detectableby the pulse generator 102, 104. In some embodiments, this comparison ofthe detected charge field strength to the charge field threshold canalso provide an indication as to the degree to which the charger 116 cancontrol the charging of the pulse generator 102, 104 or to which thepulse generator 102, 104 is within charging range of the charger 116. Insome embodiments, the threshold can identify a value corresponding to adetected charge strength that can be, for example, greater than 50% ofthe first charge field power level, greater than 75% of the first chargefield power level, greater than 90% of the first charge field powerlevel, greater than 100% of the first charge field power level, greaterthan 110% of the first charge field power level, greater than 120% ofthe first charge field power level, greater than 150% of the firstcharge field power level, greater than 150% first charge field powerlevel, greater than 200% of the first charge field power level, greaterthan 500% of the first charge field power level, greater than 1000% ofthe first charge field power level, greater than 10,000% of the firstcharge field power level, and/or any other or intermediate percent ofthe first charge field power level. If it is determined that thedetected strength of the charge field is greater than the threshold,then the process proceeds to decision state 614 wherein it is determinedif there is an additional pulse generator 102, 104. In some embodiments,this determination can include determining whether more than oneresponse was received following the query message. If it is determinedthat there is an additional pulse generator 102, 104, then the process600 returns to block 608 and proceeds as outlined above. If it isdetermined that there is no additional pulse generator 102, 104, thenthe process 600 proceeds to block 616 wherein an error is triggered andan error message is provided to the user. In some embodiments, the errormessage can indicate that no pulse generator 102, 104 was found, and theerror message can be displayed to the user.

Returning again to decision state 612, if it is determined that thedetected charge field strength and/or power is less than the threshold,then the process 600 proceeds to block 618 wherein the charge field isset to a second charge power. In some embodiments, setting the chargefield to a second charge power and/or strength can include changing thestrength of the charge power from a first non-zero strength to a second,increased strength, which strength can be, for example, the maximumcharge field strength, and in some embodiments, can include changing thestrength from a first zero strength to a second, increased strength,which strength can be, for example, the maximum charge field strength.In some embodiments, the charge field can be set to a high second chargepower such as, for example, 75% of the maximum strength of the chargefield power, 80% of the maximum strength the charge field power, 90% ofthe maximum strength of the charge field power, 100% of the maximumstrength of the charge field power, and the/or any other intermediatepercent of the maximum charge field value. Advantageously, setting thecharge field at a second charge strength and/or power can be used todetermine the proximity of the pulse generator 102, 104 to the charger116.

In some embodiments, setting the charge field to a second power canfurther include receiving charge field strength data identifying adetected power of the charge field after the charge field has been setto the second charge field power.

After the charge field presence is set to the second power, the process600 proceeds to decision state 620 wherein it is determined if the powerand/or strength of the charge field as detected by the pulse generator102, 104 is greater than a threshold. In some embodiments, thiscomparison can indicate if an adequate amount of the electrical field isdetectable at the pulse generator 102, 104 to allow charging of thepulse generator 102, 104 at a desired rate. In some embodiments, thethreshold can identify a percentage of the second charge field powerlevel such as, for example, 60% of the second charge field power level,70% of the second charge field power level, 70% of the second chargefield power level, 80% of the second charge field power level, 90% ofthe second charge field power level, 100% of the second charge fieldpower level, 110% of the second charge field power level, 120% of thesecond charge field power level, 150% of the second charge field powerlevel, and/or any other or intermediate percent of the second chargefield power level. In some embodiments, the comparison of the detectedstrength of the charge field to the second charge field power level viacomparison to the threshold can include normalizing of the detectedstrength of the charge field based on the strength of the charge fielddetected in block 610. In some embodiments, this normalization canminimize any data skew that may be caused by electric fields fromsources other than the charger 116. If it is determined that thedetected strength of the charge field is less than the threshold, thenthe process 600 proceeds to decision state 614 and proceeds as outlinedabove.

If it is determined that the detected strength of the charge field isgreater than the threshold, then the process 600 proceeds to block 622and the pulse generator 102, 104 is identified. In some embodiments,this can include storing identification information of the identifiedpulse generator 102, 104 such as, for example, storing the serial numberof the identified pulse generator.

After pulse generator 102, 104 has been identified, the process 600proceeds to block 624 wherein charge monitoring is started. In someembodiments, the starting of charge monitoring can include theinitiation of charging of the pulse generator 102, 104. In someembodiments, initiation of charging of the pulse generator 102, 104 caninclude setting the charge field to a third charge field strength. Insome embodiments, this third charge field strength can be identifiedbased on information associated with the pulse generator 102, 104including, for example, the energy storage capacity of the energystorage device 308, the charge state of the energy storage device 308,the maximum rate of charge of the pulse generator 102, 104, one orseveral field properties determined by the pulse generator 102, 104including, for example, the strength of the charge field at the firsttime and/or the strength of the charge field at the second time, and/orthe like. In some embodiments, this information can be received from thepulse generator 102, 104 as part of block 504 of process 500, and insome embodiments, this information can be retrieved from the data module402 of the charger 116. In some embodiments in which a plurality ofpulse generators 102, 104 have been detected, the third charge fieldstrength can be set to be detectable by one or several of the pluralityof pulse generators 102, 104 and to be undetectable by one or several ofthe plurality of pulse generators 102, 104. After the third charge fieldstrength has been identified, in some embodiments, the charger 116 cangenerate and send a message to the pulse generator 102, 104 indicatingthe initiation of charging. Further details of charge monitoring will bediscussed with respect to FIG. 7 below.

With reference now to FIG. 7, a flowchart illustrating one embodiment ofa process 700 for charge monitoring is shown. In some embodiments, theprocess 700 can be performed to monitor and/or to control the charging.In some embodiments, this can result in improved charging efficiency anddecreased risk of injury and/or discomfort created by the charging ofthe pulse generator 102, 104.

The process 700 continues from block 624 of FIG. 6 and proceeds to block704, wherein the charge message is received. In some embodiments, thecharge message can be received in response to a request send by thecharger 116, and in some embodiments, the charge message can be receivedby the operation of pulse generator 102, 104 according to one or severalstored protocols. In some embodiments, the charge message can includeone or both of the communication indicating completed charging orcommunication requesting an adjustment in the charge strength. In someembodiments, and as discussed with respect to block 520 and 524 of FIG.5, these messages can include one or both of a command or request forthe charger 116 to take an action, and/or data that can be used by thecharger 116 to determine whether to take an action such as, for example,stopping charging and/or adjusting the charge field strength. The chargemessage can be received by the network interface 400 of the charger 116.

After the charge message has been received, the process 700 proceeds todecision state 706, wherein it is determined if charging is complete. Insome embodiments, this determination can include determining whether thecharge message included a command/request to stop charging and/orwhether the charge message included data indicative of completeness ofcharging. In some embodiments, the completeness of charging based ondata received in the charge message can be determined by comparing thereceived data to one or several thresholds in the same manner asoutlined in process 500 of FIG. 5.

If it is determined that charging is complete, then the process 700proceeds to block 708 wherein the charge field is turned off. In someembodiments, this can include storing data relating to the completedcharging such as, for example, the identification of the charged pulsegenerator, the amount of charge provided to the pulse generator, theinternal resistance of the energy storage device of the pulse generator102, 104, the duration of the charging event, or the like. In someembodiments, this information can be used to estimate the life of thepulse generator 102, 104 and/or the energy storage device 308 of thepulse generator 102, 104. This data can be stored in the memory of thecharger 116 and/or transmitted to one or both of the clinicianprogrammer 118 and the patient remote 120.

Returning again to decision state 706, if it is determined that chargingis not complete, the remaining charge time can be estimated as indicatedin block 710. In some embodiments, this estimate can be based onprevious data collected relating to the charging of one or several pulsegenerators 102, 104, based on data received in the charge messageincluding, for example, the charge state of the energy storage device308, or the like. In some embodiments, this estimate can be generated bythe charger 116 and/or received from the pulse generator 102, 104 aspart of the charge message.

After the remaining charge time has been estimated, the process 700proceeds to decision state 712 wherein it is determined whether toadjust the charge field strength. This determination can be based on thecharge message, including information in the charge message and/or onthe estimated remaining charge time. In some embodiments, this decisioncan include identifying whether the charge message included a command orrequest to adjust the strength of the charge field and/or determiningwhether information contained in charge message correlates with criteriafor adjusting the strength of the charge message. In some embodiments,the correlation between information contained in the charge message andadjusting the strength of the charge message can be determined accordingto steps outlined with respect to process 500, and specificallyaccording to block 516 and decision state 522, which steps can beperformed, in some embodiments, by the charger 116.

If it is determined that the charge field strength should be adjusted,then the process 700 proceeds to block 714 wherein the field strength isadjusted. In some embodiments the adjustment of the charge fieldstrength can include storing data relating to the adjustment and/or thecircumstances leading to the adjustment. In some embodiments, this datacan include the amount of charge provided until the adjustment, theamount of charge time until the adjustment, or the like. In someembodiments, this information can be used to estimate the life of thepulse generator 102, 104 and/or the energy storage device 308 of thepulse generator 102, 104. This data can be stored in the memory of thecharger 116 and/or transmitted to one or both of the clinicianprogrammer 118 and the patient remote 120.

After the charge field strength has been adjusted, or returning again todecision state 712, if it is determined that no adjustment to the chargefield strength is needed, then the process 700 proceeds to block 716 andwaits until a predetermined amount of time has passed. In someembodiments, the predetermined time can comprise a percent of theestimated remaining charge time. Advantageously, by waiting a percent ofthe estimated remaining charge time, the likelihood of overcharging isdecreased. In some embodiments, the predetermined time can comprise, forexample, 25 percent of the estimated remaining charge time, 50 percentof the estimated remaining charge time, 75 percent of the estimatedremaining charge time, 80 percent of the estimated remaining chargetime, 90 percent of the estimated remaining charge time, 95 percent ofthe estimated remaining charge time, 98 percent of the estimatedremaining charge time, 99 percent of the estimated remaining chargetime, and/or any other or intermediate percent of the remaining chargetime. In some embodiments, this predetermined amount of time can becalculated by determining an estimated amount of time for the pulsegenerator 102, 104 to reach a predetermined charge state that is apercent of a fully charged charge state. In some embodiments, thispercent can be a 70 percent charge state, an 80 percent charge state, a90 percent charge state, a 95 percent charge state, a 98 percent chargestate, a 99 percent charge state, and/or any other or intermediatepercent charge state. After the process 700 has waited for thepredetermined amount of time, the process 700 returns to block 704 andproceeds as outlined above.

In the foregoing specification, the invention is described withreference to specific embodiments thereof, but those skilled in the artwill recognize that the invention is not limited thereto. Variousfeatures and aspects of the above-described invention can be usedindividually or jointly. Further, the invention can be utilized in anynumber of environments and applications beyond those described hereinwithout departing from the broader spirit and scope of thespecification. The specification and drawings are, accordingly, to beregarded as illustrative rather than restrictive. It will be recognizedthat the terms “comprising,” “including,” and “having,” as used herein,are specifically intended to be read as open-ended terms of art.

What is claimed is:
 1. A method of charging an energy storage device ofan implantable pulse generator using an external charger, the methodcomprising: wirelessly receiving at the external charger an identifiercorresponding to the implantable pulse generator; generating anelectrical field with the external charger; wirelessly receiving at theexternal charger telemetered data comprising information identifying avoltage from the implantable pulse generator corresponding to a firstsensed strength of the electrical field; changing the strength of theelectrical field at the external charger to a second strength;wirelessly receiving at the external charger information identifying atemperature of a plurality of electrical components from a temperaturesensor located proximate to the plurality of electrical components inthe implantable pulse generator and a rate of charge of an energystorage device in the implantable pulse generator; and changing thestrength of the electrical field to a third strength based on the sensedtemperature of the plurality of electrical components and thetelemetered data comprising information identifying a voltage from theimplantable pulse generator corresponding to the sensed electrical fieldstrength.
 2. The method of claim 1, wherein the external chargerinformation identifying a temperature of the at least one electricalcomponent is received after the strength of the electrical field ischanged from the first strength to the second strength.
 3. The method ofclaim 1, further comprising: wirelessly receiving information at theexternal charger from the implantable pulse generator corresponding to asecond sensed strength of the electrical field; and charging the energystorage device of the implantable pulse generator using the externalcharger.
 4. The method of claim 3, wherein charging the energy storagedevice comprises: wirelessly receiving at the external chargerinformation identifying a charge current; and changing the strength ofthe electrical field at the external charger to a third strength basedon the information identifying the charge current.
 5. The method ofclaim 3, wherein charging the energy storage device comprises:wirelessly receiving at the external charger information identifying anexcess charge current; and changing the strength of the electrical fieldat the external charger to a third strength based on the informationidentifying the excess charge current.
 6. The method of claim 5, whereinthe excess charge current comprises a shunt current.
 7. The method ofclaim 3, wherein charging the energy storage device comprises:determining with the external charger an estimated charge time based onthe information identifying the charge state of the energy storagedevice.
 8. The method of claim 7, wherein the estimated charge timeidentifies the amount of time until the energy storage device reaches apredetermined charge level.
 9. The method of claim 8, wherein chargingthe energy storage device further comprises increasing the strength ofthe electrical field at the external charger to a third strength basedon the estimated charge time.
 10. The method of claim 8, whereincharging the energy storage device further comprises: determining anamount of time based on a percent of the estimated charge time; delayingquerying the implantable pulse generator until passage of the amount oftime; and querying the implantable pulse generator for data indicativeof charge completion after the passage of the amount of time.
 11. Themethod of claim 1, further comprising, determining an inability torecharge the implantable pulse generator based on the informationcorresponding to the first sensed strength of the electrical field. 12.The method of claim 1, wherein the at least one electrical componentcomprises at least one of: an energy storage device; a resistor; or aninductor.
 13. A wireless charging system, the system comprising: animplantable pulse generator, the implantable pulse generator including aplurality of electrical components and a temperature sensor positionedto sense a temperature of the plurality of electrical components,wherein the implantable pulse generator is configured to transmittelemetered data comprising information corresponding to: (i) a sensedelectrical field strength, and (ii) the sensed temperature of theplurality of electrical components; and an external charger configuredto receive the transmitted telemetered data comprising information fromthe implantable pulse generator and to initiate charging of the energystorage device based on the sensed electrical field strength and changethe strength of an electrical field based on the sensed temperature ofthe plurality of electrical components and the sensed electrical fieldstrength.
 14. The system of claim 13, wherein the external charger isconfigured to vary the strength of the electrical field based oninformation received from the implantable pulse generator.
 15. Thesystem of claim 13, wherein the information received from theimplantable pulse generator identifies one of: a voltage; chargecurrent; or charge rate.
 16. The system of claim 15, wherein thetemperature sensor comprises one of: a thermocouple; or a thermistor.17. The system of claim 16, wherein the external charger is configuredto charge the implantable pulse generator.
 18. The system of claim 17,wherein the external charger is configured to: generate a secondelectrical field having an electrical field strength based on receivedinformation corresponding to a previously sensed electrical fieldstrength; and receive information corresponding to a second sensedelectrical field strength; and initiate charging when the second sensedelectrical field strength exceeds a threshold value.
 19. The system ofclaim 17, wherein the external charger is further configured to: receiveinformation identifying the temperature of the electrical component;compare the information identifying the temperature of the electricalcomponent to a threshold value; and decrease the strength of theelectrical field when the information identifying the temperature of theelectrical component exceeds the threshold value.
 20. The system ofclaim 13, wherein the electrical component comprises at least one of: anenergy storage device; a resistor; or an inductor.